Adjustable head for oil burners



April 27, 1954 R. L. DENNIS ETAL y ADJUSTABLE HEAD FOR OIL BURNERS FiledJan. 29, 1952 Patented Apr. 27, 1954 UNITED STATES TENT OFFICEADJUSTABLE HEAD FOR OIL BURNERS Application January 29, 1952, Serial No.268,848

7 Claims.

This invention relates to a burner head of the type primarily consistingof a fuel nozzle from which a conical spray of oil is adapted to beyprojected together with a conical stream of air into the combustionchamber of a furnace. Burners of this type have been in wide use formany years and many individual features of construction have beendevised and tried for the purpose of obtaining improved results in thecombustion of the fuel. In seeking to improve burners of this type,several objectives have usually been in view, such as economy ofoperation by complete combustion of the fuel without however,introducing into the combustion chamber excess air which would tend toreduce the temperature therein with a resultant loss in operatingefficiency. Another important objective, especially in domesticinstallations is a quiet flame which is free from pulsations orvibrations. Pulsating iiames are not only objectionable on account ofthe resultant noise but can often set up vibrations in domestic furnaceswhich may have damaging or destructive eifects on the rebrick combustionchamber or the furnace itself.

Heretofore, innovations in the structure or adjustment of burners hasbeen more or less hitor-miss, the results being judged. by such criteriaas the appearance of the flame, the presence or absence of pulsations,the density of the smoke produced, and the CO2 content of the combustiongases, the percentage of CO2 being an indication of the extent to whichthe oxygen in the air supplied to the burner is combining with the fuelin the com-bustion process. As far as We are aware, there has been noattempt made, until recently, to make a measured exploration of thepatterns of air streams projected from burners. By means of a simpleapparatus con-A sisting of a small tube arranged to be mounted with anopen end in front of a burner and its orifice toward the burner, and amanometer connected to the other end of the tube, quantitativemeasurements have been made and charted, showing significant patterns ofair now in the streams emitted by various burners and by a single burnerwith various adjustments. Photographs of ames in the nre-box show thatthe pattern of a flame closely resembles that of the air stream which isexplored when no fuel is being supplied. In making experiments todetermine the character of an air stream, the tube in the testingapparatus is mounted so that its orifice can be swung aroundV in asemicircle from one side ofthe burner orifice tothe other, readings ofthe manometer being taken for successive angular positions of the tubeorice with respect to the axis of the burner. Experiments. show thatthere are two distinct types of air patterns which are hereinafterdescribed in more detail and are referred to as the sunower type and thecandle name type. The type of pattern desirable for any particularinstallation will depend largely on the characteristics of the furnacein which the burner isinstalled and the kind' of oil to be burned. Anobject of the present invention is to provide a burner which can easilybe adjusted to give either type of' air pattern so that it can besatisfactorily installed in any kind of furnace, and can be adjustedl toburn. distilled fuel oil or the more recent catalytic fuel oils, ormixtures of the two in any proportion. In the burner hereinafterdescribed as an embodiment of the invention the main air stream withinthe burner flows between two coaxial cylinders, the outer cylinderterminating` in a frusto-conical lip. Helical vanes mounted` in thespace between the cylinders give the column of air a whirling motion sothat it emerges from the oriiioein the form of a hollow cone. The fuelnozzle is coaxialv with the cylinders and is designed to emit a hollowconical spray of fuel. If no provision is made for an inner air streamthe velocity of the main air stream and of the fuel spray sets up anarea of lowered pressure behind the fuel nozzle which results inobjectionable sporadic hare-backs. According to the present invention,the inner cylinder is. pro.- vided with a considerableY number ofperforations which admit suflicient air from the main stream to thespace around and behind the fuel nozzle to relieve the low pressurethere. This air enters the inner cylinder with no forward velocity andits subsequent flow in the axial direction is merely suflicient toprevent the development of low pressure behind the fuel nozzle. This isnot sufficient to modify the pattern of' the main stream as it emergesfrom the orifice of the burner. As hereinafter explained, the burnerthus far described is designed to produce the sunower type of air streampattern or flamein the iirebox. This type of flame is necessary for thesuccessful use of oil fuel which is wholly or predominantly of thecatalytic type produced by the use of cracking processes well known inthe art. It is also necessary for proper combustion of catalytic oilthat the emerging air stream have maximum symmetry so that all portionsof the fuel spray will be uniformly supplied found that even a slightirregularity in the air pattern results in a corresponding localinadequacy of air supply in contact with the fuel sprayed from thenozzle. If at any such point the droplets of fuel are heated above 650F. without being ignited, owing to insufficient access of air, the oilin such droplets will coke instead of burning and will escape as soot.Exploration of the air pattern of a burner reveals such irregularitiesand indicates corrective measures necessary for achieving a symmetricalpattern.

For many domestic installations the suniiower type of flame isobjectionable as it is apt to be noisy and vibratory. Hence, provisionis made for an adjustment of the burner to produce the quieter candleform of iiame. According to the invention this is done by the use ofsymmetrically arranged apertures in the rear end wall of the innercylinder with shutters to close them if desired. The shutters whenopened permit a substantial axial inner flow of air which meets andmodifies the main air stream and results in a longer flame which isnearer to the axis than the sunflower type. rIhis is due to the factthat air passing through apertures in the rear wall of the innercylinder is impelled by the static pressure of the air against the rearface of this wall and issues within the inner cylinder as jets having astrong velocity in the axial direction with a resultant modification ofthe pattern cf the main air stream. Here again it is important that theinner air stream be as regular and symmetrical as possible so that thefuel spray will be uniformly supplied with air. The shutter can beadjusted, if desired, to produce intermediate shapes of flame betweenthe extreme forms described as may be found best suited to someparticular furnaces.

For a more complete understanding of the inburner head embodying theinvention, a part being broken away to show in section;

Figure 2 is a section on the line 2 2 of Figure 1;

Figure 3 is a section on the line 3 3 of Figure l, showing the aircontrol shutter partly r closed; and

Figure '4 is a diagram indicating air patterns resulting from` differentsettings of the shutter.

The burner head includes a Cylindrical casing member fill having afrusto-con-cal lip I2 terminating in the discharge orifice iii. in theburner illustrated in Figure 1 the casing it) is shown as installedwithin a larger cylindrical casing It, thus indicating that the burnerhead can be mounted within the housing of a previously installed unit.In such cases, if the casing l is smaller than the interior diameter ofthe original casing l5, an adapter sleeve I8 maybe tted within the outercasing It to lill the clearance between the outer casing it and theburner casing le. Furthermore, the space between the forward end portionof the outer casing Il! and the lip i2 may be lled with cement 243, ifdesired. It is to be understood that the nested casings IU and i6 arevirtually a single casing with a frusto-conical terminal lip and arehereinafter referred to collectively as the outer casing or outercylinder.

A fuel supply pipe 22A is mounted within the casing Hl and is coaxialtherewith, a fuel nozzle 24 with the customary nozzle adapter 25 beingmounted on the discharge end of this pipe. As indicated, this pipe maybe bent so as to extend out through a slot 26 in the wall of the casingi6. Suitable nuts 28 and Sii may be threaded on the portion of the pipeprojecting through the slot 2E, these nuts being tightened to secure thesupply pipe and its nozzle in any position of coaxial adjustment.

An inner cylinder 32 is supported within the casing I0 coaxiallytherewith. rthis cylinder is entirely open at its forward end with nolip or constriction, but is provided with a wall or plate 3d at its rearend. The wall is supported by a transverse frame member 36 having acollar 3B integral therewith, the fuel pipe 22 iitting in a bore throughthe frame 36 and collar Sii. The inner cylinder 32 is thus convenientlysupported on the fuel pipe 22 and is adjustable axially thereon. A setscrew di) serves to secure the inner cylinder in any adjusted positionon the fuel pipe 22. The length of the sleeve 38 is carefully determinedso that when its forward end face is engaged by the rear end of thenozzle adapter 25, then the nozzle 24 will be properly located withrespect to the forward end of the inner cylinder 32. Thus the forwardface of the collar 33 acts as a gauge or stop for the nozzle adapterwhenever the nozzle with its adapter is removed and replaced.

The cylindrical wall of the cylinder 32 is preferably perforated asindicated at 42, a large number of relatively small perforations beingindicated in Figure 1. These permit the infiltration r of air withoutinitial axial velocity into the inner cylinder to prevent the buildingup of low pressure within this cylinder.

The rear wall 34 is provided with a series of relatively large aperturesfifi, these apertures preferably being in the form of narrow sectorssymmetrically arranged around the axis of the cylinder as indicated inFigure 2. A shutter te in the form of a disk is i'ltted against the rearface of the wall 34 and is rotatable through a sufficient angle to openor tightly close the apertures et, the shutter disk it having similarapertures arranged to register simultaneously with all the apertures 44when the shutter is moved to the opened position. The shutter is movableto a closed position in which it closes all of the apertures ed and thuscompletely shuts on any flow of air through the rear wall 34. A setscrew @is extends through an arcuate slot 5e in the shutter disk 46 andis threaded into the wall 313. When this screw is set up, it secures theshutter in any position of adjustment.

Ignition means for the burner includes electrodes in the form of a pairof insulated rods or heavy wires 52 which have bare end portions 54 thetips of which are suitably spaced to provide a spark gap near the oriceof the fuel nozzle 24. For minimum interference with the uniformdistribution of the air stream within the inner cylinder when theapertures M are open, the electrodes 52 are arranged symmetrically withrespect to the axis of the inner cylinder 32 and fuel pipe 22, that is,they pass through the rear wall 3d and frame 3e at points equally andoppositely spaced from the axis of the fuel pipe, as indicated inFigures 2 and 3. The electrodes are also preferably as small as isconsistent with the functions they must perform.

Theicasing i0 carries on its inner surface a series of helical vanes (i0which cause the main air stream owing in the space between the casingand the inner cylinder 32 to form a conical pattern as it emerges fromthe orifice Ill. The diameter of the inner cylinder 32 is preferablyequal' to or greater than the orifice le. By axially adjusting theposition of the inner cylinder 32', the clearance between its forwardend and the inner surfaceof the lip l2 can be varied so as toV chokeVthe main stream of air if desired.

When a conical' stream of air flows from the orifice le the shutter 4Sbeing closed, the forward and outward velocity of the air tends to lowerthe air pressure within the cone, this area of lowered pressure beingnear the orifice le and being distinct from the low pressure area whichis formed back of the fuel nozzle unless relieved by some means such asthe perforations 42.

The small amount of air which enters the inner cylinder through theperforations #32 to prevent back fash of the flame within the innercylinder is insufficient in amount to affect the `pattern f the main airstream. 'Ihe resulting iiame is of a frusto-conical shape and is hereinreferred to as the sunower type of flame. A flame of this type,especiallyT when symmetrical in shape and free from irregularities,indicates a relatively high efficiency of combustion and in general isnecessary for the proper combustion of fuel oils which are largely orwholly of the catalytic type. The sunflower type of flame is usuallysomewhat noisy and therefore objectionable in some domesticinstallations where a quiet flame is highly desirable. By adjusting theshutter disk 4S to open the apertures 44 partly or fully, the nature ofthe flame can be radically changed, the resultant flame being longer andnarrower so as to resemble more nearly a candle flame. Such a flame isrelatively quiet and may be nearly as efficient as the sunflower typebut usually cannot be employed for fuel oils containing a highpercentage of catalytic oil. The elongated flame results from the factthat the main air1 stream is modified by the inner air stream whichenters the rear end of the inner cylinder 32 with considerable axialvelocity and emerges from the open forward end of the inner cylinder tomix with the main air stream, there being no transverse obstructions inthe inner cylinder forward of the frame 35. If the apertures 44 arefully opened the inner air stream is of considerable volume as Well asvelocity and materially alters the shape of the flame. in extreme caseswhen an extra large flow is desired in the inner stream, the shutter deand plate 34 can be removed, leavthe rear end of the inner cylinderfully open.

The air patterns for the open and closed positions of the shutter areindicated on the chart shown in Figure e. This chart was prepared byactual experiment, the dot and dash lines E52 representing the airpressures registered at the orifice of the testing apparatus when theburner w s operated without fuel and with the apertures it fuily closed.rihe solid line curve te represents the air pressures at various anglesthe stream emerging from the orifice H! when the apertures were fullyopen. Readings were taken on a manometer connected to a small tube whichwas mounted on a bracket in such a way that its oriiice would face thedischarge le, the orifice of the tube being spaced a short distance awayfrom the orifice i4, the bracket supporting the tube permitting theadjustment of the-tube to positions of any angularity from directly inline with the axis to positions 90 away on either side. The resultingcurves illustrated by the dot and dash lines 62 in Figure 4 indicatethat when the 6 apertures M are fully clos'ed-, the main stream of airemerges ina sharply defined hollow cone. The graph show-n is notcomplete since the pressures indicated at and near the axis' wereactually negati-ve, that is, below atmospheric pressure. Hence, suchpoints on the graph would be off the chart.

When the apertures M' are wide open, the resultant air stream emergingfrom the orifice le has maximum pressure near the a-xi's and quicklyfalls off to a negligible pressure from 10 to 25 from the axis.

The shutter disk thus permits adjustment of the name to the sunflowertype or the candle name type or to any intermediate shape between thesetwo extremes as may be required for any particular installation. Therelative volumes of now of the main and inner 'air streams can furtherbe regulated by coaxial adjustment of the inner `cylinder 32 toward orfrom the lip l2. Since the diameter of the inner cylinder is preferablyat least equal to or somewhat greater than the diameter of the orificelli, it is evident that adjustment of the inner cylinder forward to aposition in which its forward end is close to the lip le could result inchoking the main air stream to such an extent that its ow may benegligible in comparison with that of the inner air stream. Thus a widevariation of air streams can be had by adjusting the inner cylinder andthe shutter disk.

It is highly important that, whatever positions of adjustment the innercylinder and shutter disc may have, turbulence within the burner head bekept at a minimum so as to avoid as far as possible irregularity andnoise in the air stream and flame within the rebox. For this reason theapertures 44 are evenly and symmetrically distributed over the rear wallof the inner Icylinder and the perforations 112 are evenly distributedover the cylindrical wall of the inner cylinder. Furthermore, theelectrodes 52 are for the same purpose symmetrically arranged ashereinbefore described.

We claim:

1. A burner head for liquid fuel comprising: a cylindrical casing; aninner cylinder coaxial within said casing and defining therewith anannular air passage; a frusto-conical lip at the discharge end of saidcasing axially and circumferentially overlapping helical vanes in saidpassage contacting the inner surface of said casing and the outersurface of said cylinder; transverse means across the rear end of saidcylinder and having a plurality of aperture means therein extendingsubstantially across the same for axial ow of air therethrough;laterally adjustable shutter means controlling said aperture means andoperable to completely shut off the axial fiow of air into said cylinderthrough said transverse means; a fuel supply pipe extending through saidtransverse means and coaxial with said casing; and an atomizing fuelnozzle mounted on said pipe ycoaxially within said cylinder adjacent theforward end thereof.

2. The structure defined in claim l in-which the inner cylinder has aplurality of small perforaticns therein for passage of air therethroughinto said cylinder to avoid low pressure therein rearwardly of thenozzle orifice when the aperture means are closed by the shutter means.

3. The structure defined in claim 2 in which the aperture means arearranged symmetrically about the axis of the inner cylinder.

4. The structure defined in claim 2 in which the diameter of the innercylinder is at least as large as that of the minor diameter of the lip.

5. The structure dened in claim 2 in which the lip is smooth-Walled.

6. The structure defined in claim 2 in which the vanes are disposedentirely rearward of the lip.

7. The structure dened in claim 2 in which the inner cylinder is ofuniform diameter throughout its entire length.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date Rief et a1 June 27, 1939 Vollmer Nov. 28, 1939 GlendenningJan. 29, 1946 Hannah Apr. 5, 1949 Bernhard July 15, 1952

